| With the development of communication technology, how to carry out reliable communication with good error-correcting code at low signal noise ratio is a problem people focus on. In the context of the iterative system, the LDPC(Low Density Parity Check) code is introduced as the error-correcting code, and the TMS320C6747 DSP of TI company is used for the implementation of LDPC encoder and decoder at low signal noise ratio in Gaussian white noise channel.The basic principle of LDPC code and the concept of Tanner figure are presented, and the construction of LDPC check matrix is studied, especially the features of QC_LDPC code. Several encode and decode algorithms are elaborated in detail, and their features and merits are studied and compared. Combined with the performance indicators of the thesis, some related parameters of implementation are analyzed through computer simulation, such as check matrix, encode and decode algorithms, code length, and frequencies of iterations, etc.According to the design program and related parameters, the LDPC encode and decode algorithms implement combined with DSP which works as implementation platform. On encoding, the iterative rapid encode algorithm is selected to reduce encoding delay and complexity. In terms of decoding implementation, in order to overcome the shortcomings of the high complexity of the BP decoding algorithm's hardware implementation, some improvements about the hardware memory and the disposing of data precision was proposed, and the implementation of the QC_LDPC decoder based on the BP algorithm was completed in the end.In Gaussian white noise channel, the iterative system with LDPC encoder and decoder is tested BER at several signal noise ratio, whose test platform is realized by software VC6.0 in computers. The test results show that the system reaches the performance requirements. |
